The present invention relates to an improvement of a linear ultrasonic motor generating longitudinal and transverse motion.
Ultrasonic motors are broadly classified into travelling-wave types and standing-wave types.
The principle of operation of the standing-wave type ultrasonic motor is to abut a moving member with specified pressure, against an ultrasonic vibrator exciting substantially an elliptical movement to drive a moving member by a frictional force between mass points on the ultrasonic vibrator, which are elliptically vibrating and the moving member.
The standing-wave type ultrasonic vibrator is easy to construct such that it realizes highly efficient vibration. Accordingly, the standing-wave type motor is advantageous for obtaining high efficiency and large output compared with the travelling-wave type motor.
The ultrasonic vibrator used for a conventional standing-wave type motor employs a mechanical resonance type vibration of normal mode which makes a single-directional vibration on the contact surface of an elastomer with an exciter while making an elliptical vibration on the contact surface of an elastomer with a moving member in order to excite a highly efficient elliptical movement.
The conventional ultrasonic motor is classified into a rectilinear and a curvilinear type. An example is shown in FIG. 6.
A linear ultrasonic motor 31 is constructed such that a drive unit 32 provided in an ultrasonic vibrator 11 is pressed against a rail 34 by a support member 33. Roller bearings 35 are fixed to the both ends of the support member 33. Support bases 61 are fixed to the both ends of the rail 34. The support bases are provided on a base 62. An ultrasonic wave transmitter-receiver 63 is fixed to a part of the rail 34 for transmitting and receiving ultrasonic vibration.
In this linear ultrasonic motor, there is a problem of side-slip or running of a moving member, necessitating some support mechanism. A support mechanism supports the sides of the rail therebetween via rollers, thereby largely increasing the weight of the moving member and deteriorating the responsiveness. Moreover, the structure becomes complicated and unnecessary vibration occurs.